In previous studies we have described various aspects of the dispersion, chromatographic behavior, and kinetics of various adenylate cyclases. We have described properties of membranes and of ATP-regenerating systems commonly used in the assay of adenylate cyclase that can lead to artifacts in measured cyclase activity. We developed an enzymatic procedure for preparing (alpha-32P)ATP, the substrate of choice for adenylate cyclase. In pursuing the characteristics of the regulation of adenylate cyclase by adenosine in platelets and striatum we have demonstrated a GTP-dependent stimulation by adenosine that is additive with stimulatory or inhibitory effects of catecholamines, suggesting distinct coupling mechanisms for the respective receptors with the adenylate cyclase. Our immediate objectives in the proposed studies are: a) to define better the phospholipid requirements for the coupling of the adenosine and dopamine receptors to the adenylate cyclase; b) to develop labeled and unlabeled analogs of adenosine useful in photo-affinity coupling to adenosine binding proteins; c) to evaluate the usefulness of tritiated analogs of adenosine for identifying adenosine binding proteins; and d) to utilize available adenosine-Sepharoses for the isolation of such adenosine binding proteins.